Immobilization of trivalent actinides by sorption onto quartz and incorporation into siliceous bulk: Investigations by TRLFS

Stumpf, S.; Stumpf, Th.; Lützenkirchen, Johannes; Walther, Clemens; Fanghänel, Th.

doi:10.1016/j.jcis.2007.09.080

Cited by 40 publications

(33 citation statements)

References 30 publications

(29 reference statements)

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“…Consequently, a reliable understanding of their behaviour in contact with surfaces is crucial whenever retention processes are to be taken advantage of in the Safety Case for a given repository. Extensive studies have been carried out on the uptake of trivalent actinides onto mineral surfaces under different conditions [13][14][15][16][17][18] , but a study for high salt content on silica minerals is missing. In Germany and some other countries (Canada, USA, etc.)…”

mentioning

confidence: 99%

Sorption of Eu(III) on quartz at high salt concentrations

Garcia

Lützenkirchen

Петров

et al. 2019

Colloids and Surfaces A: Physicochemical and Engineering Aspect

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Sorption of Eu(III) onto quartz from highly saline solutions (up to 5M NaCl) has been studied by sorption edges. The acid-base titrations of the solid surface suggest the rather unusual presence of two different sites that has been the object of recent discussions in the literature. Europium uptake results show the usual behaviour with a steep pH-edge and nearly complete removal at sufficiently high pH. Previous spectroscopic data on this system suggest the presence of two bidentate surface complexes with different proton stoichiometry. Based on this, a self-consistent Surface Complexation Model (SCM) was fitted to the full set of experimental data, from 0.1 to 5 M NaCl, using a coupled Pitzer/surface complexation approach. The Pitzer model was applied to aqueous species. A Basic Stern Model was used for interfacial electrostatics of the system, which includes ion-specific effects via ion-pair formation. Parameter fitting was done using the general parameter estimation software UCODE coupled to a modified version of FITEQL2 involving separate calculations of the respective ionic strength corrections. At high ionic strength (>1 M), the surface potential is strongly screened by ion-pair formation and the diffuse layer potential is negligibly low, which justifies the extension of the standard electrostatic model to these harsh conditions. Overall, our model is able to describe the full set of analysed data. It is expected that these first systematic data acquisition along with the detailed modelling can serve as a benchmark for the modelling of future studies on sorption in highly saline systems.

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mentioning

confidence: 99%

Sorption of Eu(III) on quartz at high salt concentrations

Garcia

Lützenkirchen

Петров

et al. 2019

Colloids and Surfaces A: Physicochemical and Engineering Aspect

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“…Generally, nonelectrostatic models will require more surface species than models including an electrostatic correction term. Also the electrostatic factors include pH-dependence (Stumpf et al 2008), so that they help outcompete hydrolysis reactions in solution. Insofar, calculated surface speciation is to some extend speculative.…”

Section: Sorption Onto Illite (Illite Du Puy)mentioning

confidence: 99%

“…An electrostatic model might predict stronger uptake for all ionic strengths with increasing pH. For example, Stumpf et al (2008) estimated that the formation constant for an inner-sphere surface complex would increase by one order of magnitude for each positive charge unit that is transferred to a negative surface. Since this is compatible with our system (i.e.…”

Section: Sorption Onto Illite (Illite Du Puy)mentioning

confidence: 99%

Sorption of Cm(III) and Eu(III) onto clay minerals under saline conditions: Batch adsorption, laser-fluorescence spectroscopy and modeling

Schnurr

Marsac

Rabung

et al. 2015

Geochimica et Cosmochimica Acta

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The present work reports experimental data for trivalent metal cation (Cm/Eu) sorption onto illite (Illite du Puy) and montmorillonite (Na-SWy-2) in NaCl solutions up to 4.37 molal (m) in the absence of carbonate. Batch sorption experiments were carried out for a given ionic strength at fixed metal concentration ([Eu] total = 2 × 10-7 mol/kg, labeled with 152 Eu for γ-counting) and at a constant solid to liquid ratio (S:L = 2 g/L) for 3 < pH m < 12 (pH m =-log m H+). The amount of clay sorbed Eu approaches almost 100% (with log K D > 5) for pH m > 8, irrespective of the NaCl concentration. Variations in Eu(III) uptake are minor at elevated NaCl concentrations. Time-resolved laser fluorescence spectroscopy (TRLFS) studies on Cm(III) sorption covering a wide range of NaCl concentrations reveal nearly identical fluorescence emission spectra after peak deconvolution, i.e. no significant variation of Cm(III) surface speciation with salinity. Beyond the three surface complexes already found in previous studies an additional inner-sphere surface species with a fluorescence peak maximum at higher wavelength (λ ~ 610 nm) could be resolved. This new surface species appears in the high pH range and is assumed to correspond to a clay/curium/silicate complex as already postulated in the literature for kaolinite. The 2 site protolysis non-electrostatic surface complexation and cation exchange sorption model (2SPNE SC/CE) was applied to describe Eu sorption data by involving the Pitzer and SIT (specific ion interaction) formalism in the calculation of the activities of dissolved aqueous species. Good agreement of model and experiment is achieved for sorption data at pH m < 6 without the need of adjusting surface complexation constants. For pH m > 6 in case of illite and pH m > 8 in case of montmorillonite calculated sorption data systematically fall below experimental data with increasing ionic strength. Under those conditions sorption is almost quantitative and deviations must be 3 discussed considering uncertainties of measured europium concentrations in the range of analytical detection limits.

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“…This option allows for a very general treatment of data. Such a strategy has been performed for example by Lützenkirchen et al 64 or Stumpf et al 65 Titration results in terms Δc d vs. log c(H + ) do look suspicious when in the near neutral pH range tiny additions of protons or hydroxide ions are sufficient to cause large changes in pH. In such a case the titration is similar to the blank, and this causes the difference between surface titration and blank to be the difference between too similar numbers, which in turn results in large relative "experimental" errors.…”

Section: Further Consideration and Potential Problems When Using Titrmentioning

confidence: 99%

Potentiometric Titrations as a Tool for Surface Charge Determination

Lützenkirchen¹,

Preočanin²,

Kovačević³

et al. 2012

Croat. Chem. Acta

104

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Abstract. This article summarizes methods for determining proton surface charge at mineral/water interfaces. It covers conventional experimental procedures and discusses problems with the techniques. Also it involves recommendations for obtaining reasonable and comparable results. The term "comparable results" refers to comparison between results for the same solid as obtained in different laboratories. The most important parameters for the surface titrations are discussed. We also propose a reference titration procedure that would allow direct, unbiased comparisons of experimental data. The article finally includes a check-list for researchers and reviewers which should allow limiting the amount of titration data that are not useful for future uses. (doi: 10.5562/cca2062)

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Immobilization of trivalent actinides by sorption onto quartz and incorporation into siliceous bulk: Investigations by TRLFS

Cited by 40 publications

References 30 publications

Sorption of Eu(III) on quartz at high salt concentrations

Sorption of Eu(III) on quartz at high salt concentrations

Sorption of Cm(III) and Eu(III) onto clay minerals under saline conditions: Batch adsorption, laser-fluorescence spectroscopy and modeling

Potentiometric Titrations as a Tool for Surface Charge Determination

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